...Harry Potter and the Goblet of Fire (toward the end) and HOLY CRAP! Barty Crouch Jr. was David Tennant! I saw the whole movie in the theater when it came out and never noticed him. I didn't think I'd ever seen him before he became the Doctor.
(For the record, I think this and #3 are the best Potter movies thus far, but I haven't seen 6 yet and don't hold out great hopes for it or 7, because books 5 thru 7 are just too damn huge to do very well).